THE MINOR PLANET BULLETIN - MinorPlanet.Info

123
ASTEROID LIGHTCURVE ANALYSIS AT
RICKY OBSERVATORY
Craig Bennefeld
Physics Dept., Imagine Renaissance Academy
414 Wallace
Kansas City, Missouri. 64125
craig.bennefeld@imagineschools.com
Science Department Students
Vanessa Aguilar, Terrance Cooper, William Hupp,
Jeanne Pecha, Elysabeth Soar
(Received: 2009 Apr 15)
Lightcurves for six asteroids were obtained at Ricky
Observatory from 2007 October through 2008 January:
802 Epyaxa, 1666 Van Gent, 2320 Blarney, 2358
Bahner, 2509 Chukota, 3416 Dorrit.
Observations of the 6 asteroids were carried out at Bennefeld’s
Observatory (MPC H46), which is equipped with a 0.35m Meade
LX200 GPS telescope operating at f/6.3 coupled to a SBIG ST7-
XME CCD camera, resulting in a resolution of ~1.7 arcsec/pixel
(binned 2×2). Unfiltered exposure times varied between 30-60 s.
The asteroids under observation were selected from the list of
asteroid lightcurve photometry opportunities which is posted on
the Collaborative Asteroid Lightcurve Link (CALL) website
(Warner, 2007a). The students measured the photometric
properties of the images using Brian Warner’s MPO Canopus,
which employs differential aperture photometry to produce the
raw data (Warner, 2007b). Period analysis of the raw data was
done using Canopus, which incorporates the Fourier analysis
algorithm developed by Harris (Harris et al., 1989). As well as
reporting the synodic rotational period, amplitude, and phase angle
of the asteroids, every attempt was made to expand on the
knowledge base of the asteroids by, where appropriate, reporting
the minimum axial ratio a/b of an elliptical asteroid and the Phase
Angle Bisector longitude and latitude, PAB L and PAB B ,
respectively.
802 Epyaxa. This main-belt asteroid was sampled 434 times over
3 nights to achieve a synodic rotation period of 4.389 ± 0.001 h.
The absolute value of the peak-to-peak magnitude differential
(∆m) of 0.58 mag implies an axial ratio (a/b) of 1.70, assuming an
equatorial viewing aspect. The period agrees with Warner (2009).
1666 van Gent. The main-belt asteroid was sampled 156 times
over 2 nights to yield a synodic rotation period of 4.166 ± 0.003 h.
The absolute value of the peak-to-peak magnitude differential
(∆m) of 0.50 mag implies an axial ratio (a/b) of 1.58. No other
lightcurves for this asteroid are known to exist.
2320 Blarney. The main-belt asteroid was sampled 154 times over
a single night to yield a synodic rotation period of 5.097 ± 0.001 h.
The absolute value of the peak-to-peak magnitude differential is
0.44 mag, implying an axial ratio (a/b) of 1.50. No other
lightcurves for this asteroid are known to exist.
2358 Bahner. This main-belt asteroid was sampled 226 times over
a 4 night period to yield a synodic rotation period of 14.194 ±
0.002 h. Due to an incomplete data set, the axial ratio was not
computed. Behrend (2009) reports a provisional period of 10.848
± 0.003 h and Owings (2009) a period of 10.855 h. We did test our
data against the shorter period but found a lower RMS fit for the
longer period. Given the lack of consecutive nights and the
incomplete coverage of the curve in our data set, we admit that our
solution may not correct and so present it here more for the
purpose of putting our data on record.
2509 Chukotka. This main-belt asteroid was sampled 431 times
over a 4 night period to yield a synodic rotation period of 3.19 ±
0.01 h. Due to the poor SNR and the inconclusive nature of the
lightcurve, no attempt was made to calculate the axial ratio. No
other lightcurves for this asteroid are known to exist.
3416 Dorrit. This Mars-crossing asteroid was sampled 247 times
over a 2 night period to yield a synodic rotation period of 2.714 ±
0.003 h. The absolute value of the peak-to-peak magnitude
differential is 0.38 mag, implying an axial ratio (a/b) of 1.42. No
other lightcurves for this asteroid are known to exist.
Acknowledgements
The students would like to thank the entire staff at Imagine
Renaissance Academy (Wallace Campus) including Mrs. Debbie
Jones-Fowler, Head of Schools, Mr. Geoffrey Alderman, Assistant
Director, and Mr. Greg McGhee, Activities Director, for striving
to provide us with a project-based learning environment second to
none. Thanks also go out to Mr. Brian D. Warner for his input in
the preparation of this paper and finally to Mr. Bennefeld our
Physics and Astronomy teacher.
References
Behrend, R. (2009). “Asteroids and Comets Rotation Curves,
CdR.” http://obswww.unige.ch/~behrend/page4cou.html.
Harris, A.W., Young, J.W., Bowell, E., Martin, L.J., Millis, R.L.,
Poutanen, M., Scaltriti, F., Zappala, V., Schober, H.J., Debehogne,
H., and Zeigler, K.W., (1989). “Photoelectric Observations of
Asteroids 3, 24, 60, 261, and 863.” Icarus 77, 171-186.
Owings, L.E. “Lightcurves for 155 Scylla and 2358 Bahner”.
Minor Planet Bul. 36, 51-52.
# Name
Date Range
(mm/dd)
Data Pts Phase PAB L PAB B
Per
(h)
PE Amp AE
802 Epyaxa 11/15-18/2008 434 6.05 104.4 7.6 4.389 0.002 0.58 0.02
1666 van Gent 12/31/2008-01/01/2009 156 18.57 66.3 0.5 4.166 0.003 0.50 0.03
2320 Blarney 01/01/2009 154 1.66 103.2 -3.9 5.097 0.001 0.44 0.02
2358 Bahner 10/26-11/25/2008 226 13.50 12.9 6.8 14.194 0.001 0.44 0.01
2509 Chukotka 09/29-10/29/2008 431 14.3 358.2 1.4 3.19 0.01 0.16 0.03
3416 Dorrit 11/19-11/20/2008 247 19.03 31.9 12.1 2.714 0.003 0.38 0.03
Minor Planet Bulletin 36 (2009)